Perhaps a regular user of the station could enlighten me. I know that
there are no "Fast Ticket Machines" present at the station which will
issue tickets for travel on Chiltern Trains, or other train journeys,
but does the London Underground ticket machine in the main station
entrance sell such tickets ? For instance, could one buy a South
Ruislip to Aylesbury ticket or say a South Ruislip to Brighton ? I
was witness to a polite discussion between a Gripper and customer on a
Chiltern Train late last night where the passenger showed a "permit to
travel ticket" whereupon the gripper kindly informed him that you can
buy a range of tickets to Chiltern stations ( also with Railcard
discounts ) from the London Underground machine. There is a fast
ticket machine at West Ruislip on the London bound Chiltern platform
and I have occasionally used that on the assumption that the LU
machine upstairs in the main foyer could not sell me discounted
tickets to Chiltern stations.

cheers
uc